Institut Molécules et Matériaux du Mans, UMR CNRS 6283, Le Mans Université, 72085 Le Mans, France.
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Chem Phys. 2020 Jan 7;152(1):014202. doi: 10.1063/1.5135982.
We demonstrate that time-domain Brillouin scattering (TDBS), a technique based on an ultrafast pump-probe approach, is sensitive to phase transitions and apply it to the study of structural changes in 8CB liquid crystals at different temperatures across the isotropic, nematic, smectic, and crystalline phases. We investigate the viscoelastic properties of 8CB squeezed in a narrow gap, from the nanometer to submicrometer thickness range, and conclude on the long-range molecular structuring of the smectic phase. These TDBS results reveal that confinement effects favor structuring of the smectic phase into a crystallinelike phase that can be observed at wide distances far beyond the molecular dimensions.
我们证明了基于超快泵浦探测方法的时域布里渊散射（TDBS）技术对相变敏感，并将其应用于研究 8CB 液晶在各向同性、向列相、近晶相和晶相之间不同温度下的结构变化。我们研究了在纳米到亚微米厚度范围内被挤压在狭窄间隙中的 8CB 的粘弹性性质，并得出了关于近晶相的长程分子结构的结论。这些 TDBS 结果表明，限制效应有利于将近晶相结构化成为类似于晶体的相，这种相可以在远远超出分子尺寸的大距离处观察到。
